In recent years, as a base or platform of carrying out scalable Web applications, attention is drawn to the so-called cloud utilizing a number of computers within a data center. As one of the infrastructures of such a cloud, Key-Value Store (to be referred to as “KVS” hereinafter) is known. KVS is a database for managing records composed of the pair of key and value. The following Patent Document 1 discloses a computer system having KVS. In this computer system, KVS is utilized as a cache device for caching data of databases in the server. The following Patent Document 2 discloses a database system having KVS. It is disclosed that this database system has a mechanism for combining data by introducing an attribute relationship between the data of KVS. The following Nonpatent Document 1 discloses a transaction processing system in which a management node is provided to manage the right of access to KVS.
[Patent Document 1] JP 2011-8451 A
[Patent Document 2] JP 2011-13923 A
[Nonpatent Document 1] Sudipto Das, Divyakant Agrawal and Amr El Abbadi. G-Store: A Scalable Data Store for Transactional Multi Key Access in the Cloud. In Socc' 10, 2010.
However, in KVS, atomicity is supported for data manipulation on a single record. Therefore, when carrying out a transaction process utilizing KVS, if atomicity is to be ensured, then because the transaction process is carried out according to each single record, processing efficiency will come down. Further, although the above-mentioned Nonpatent Document 1 discloses a method for managing the right of access to a plurality of record groups, with this method, however, not only a management node has to be further provided, but also it is necessary to carry out a process between the management node and other nodes to aggregate access rights into the management node as a preprocess before carrying out the transaction process. Thereby, the configuration becomes complicated.